The trend in microelectronic circuitry is to implement new circuitry which will increase the performance speed, have higher density and provide increased functions with maximum reliability. MOS and CMOS devices have been used to implement circuitry which continually meet the industry demands. MOS and CMOS devices, which comprise a semiconducting substrate under the active area, have undergone structural improvements that electrically isolate the active area of the MOS and CMOS device in order to extend the performance limits of these devices, by example for improving parameters such as the junction capacitance. The term used in the semiconductor industry to describe an isolated active semiconductor structure is silicon on insulator, abbreviated as SOI. Since the active region of the SOI device is electrically isolated, the active region of the device is said to be floating. The floating characteristic, or floating body effect, results in instability of the voltage potential of the device and in a small drain-to-source breakdown voltage. Devices to reduce the floating body effect have been proposed. Noteworthy is a structure proposed in an article entitled "Body-Contacted SOI MOSFET Structure with Fully Bulk CMOS Compatible Layout and Process" by Yo-Hwan Koh, et al., IEEE Electron Device Letters, Vol. 18, No. 3, March 1997. While the Koh, et al. proposed device suppresses the floating body effect, a need is still seen to exist for a semiconductor device that not only has the benefits of an SOI device and that minimizes the floating body effect, but is not burdened by the cost of the SOI substrate, such as the commercially available SIMOX wafers utilized in the Koh, et al. proposed device.
Thus, a primary object of the present invention is to provide a semiconductor integrated circuit device fabricated on a substrate having an active device region isolated from the underlying substrate similar to a silicon on insulator(SOI) substrate structure.
A related object of the present invention is to provide an inexpensive semiconductor integrated circuit device fabricated on a substrate having an active device region isolated from the underlying substrate similar to a silicon on insulator(SOI) substrate structure and also having a reduced floating body effect.